"Whereas in the past on a slippery climb the Trac would keep the vehicle from spinning out of control but also wouldn't allow any forward movement. Now the spinning is kept to a minimum but forward motion is allowed."

I beg to differ on your statement about RWD in snow. I've logged almost three quarters of a million miles in the last 28 of driving in Northern NY. Some RWD vehicles are excellent in the snow. Some do require studded snow tires. I should remind you that rear-engine RWD's are better in snow than FWD. FWD is fine for not getting stuck but can leave you in the ditch quite quickly if caught unaware at speed. Physics dictates that have the drive force and the steering force applied to the same wheels is not the optimum setup for handling. It may be optimum setup for fuel economy.

I think we could argue about the advantages of drive location until we were all blue in the face. It seems to me with over 40 years driving in "the great white north", that the best setup is a 50/50 weight bias. However, the biggest factor is the driver, and second the tires. I've driven a vehicle with "summer tires" in snow, and was able to keep it on the road when no-one else could. I used my "secrets" gleaned from experience (also used by many other drivers, and some are teachable - I know because certain bus drivers taught me ). I wouldn't do this however, by choice. I do drive front or rear wheel drive vehicles with -proper- snow capable tires in any conditions, but only if I have to. There are too many "loose nuts" on the road to take unnecessary chances. Currently I like Nokian WR tires. They are left on year round, wear very well, and perform adequately in snow and ice. Not yet on a Prius, as I will not have mine for a few months, but when I get it count on the fact I will properly equip it with Nokians.

Name me one or two or any RWD rear engine cars. You are not talking traditional cars or trucks. What are you driving a Carrera 4 ?

90-95% of cars have the engine in the front. A lot of the traditional cars are now FWD probalby around 2/3s. Sport cars: BMW, Lexus, Infinti are front engine RWD and do not get around very well in the snow.

Yes, if you gat a truck or car and load the trunk with a lot of weight that RWD will work in the snow. Especailly with studded snow tires.

Oh yeah I know FWD is not good for dirivng and traction. Had a GSR Integra with CAT back and cold air intake and it was awesome for FWD. But yes I will agree , I have an S2000 RWD that has awesome handling.

"Toyota engineer/trainer last Nov just before the revamped '06 came out."

Hmmm, I would like to hear from some owners who have gotten out of snow in their 2006 Prius before I render judgement. For one thing, having an engineer say they put in a change doesn't mean that the change will work sufficiently or correctly to fix the problem. Such a determination requires test results under actual conditions.

"What are the actual, documented tests, that are being cited that say they are "difficult" in snow "

I consider owner's reports on this forum to be documentation. It was here that I first read of the "immobility" problem in snow with the Gen 2 Prius. I haven't seen posts indicating that the problem is fixed.

BTW, if was this 2006 modification a software change? Maybe the Prius can be flashed to correct the issue?

I do agree with the 50/50 weight bias. I live on the Tug Hill Plateau near a place that frequently makes the national news for most snowfall. I'm not faithfull to any one brand of tire. I usually by the lest expensive snowtires and have them studded, all four of them. With this setup you can drive anything in the snow. To be honest, one of the best cars I ever had for snow driving was a 1983 Chevy Camaro with a 6 cylinder. I wouldn't have dared try it with the 8 cylinder. Weight distribution is important but if you've got too much tork it won't get out of it's own way on the ice. I'm glad these forums exist because I was seriously thinking about buying a Prius. My mother had two Honda Insights and she loved them. With the problems I've read about in here about the Prius I think I'm going to go with a more conventional vehicle. Gas mileage is important but I need something that I or my amatuer mechanic can do some of the repairs to.Hopefully Toyota will continue to work out the bugs. The brake problems I've read about were the deal-breaker.

Well what they say over there is that the car simply won't move if it gets into a slippery snow condition...it just sits there and does nothing. So at that point, if they are right, then tires are irrelevant, once they've given up their grip and the computer takes over.

Supposedly this traction control system does not work the same as on regular cars. I'm just passing on second-hand info, I don't have a clue. I would like to try a Prius in the snow however to see what's what and if driver skills really is the problem or not.

Your post is absolutely correct. The car just sits there and does nothing and has nothing to do with driver skills. The traction control IS different from other cars due to the fact that its primary purpose is to protect the electric motor from over reving and possible burnout.I have been through 3 upstate new york winters living with this. I do not plan on another. I hope this is good advice for those considering a Prius.

I rented a (2005) Prius while on vacation in Arizona this year. While visiting the Grand Canyon I experienced difficult snow and ice conditions. There were many vehicles (mostly SUVs, go figure) in ditches. During that whole day I only experienced one problem and that was more engine braking than I wanted while creeping down an icy hill. What I found was that the front wheels were rotating and skidding at the same time because of engine braking, that is to say the indicated speed was about 10MPH but I was descending the hill faster than that. In the end I had to select neutral so that I could achieve balanced braking from all four wheels.

Reading between the lines, I would say that the HSD system has a snow/ice traction control bug.

And another commnet the 50/50 weight is being touted for the wrong reasons. 50/50 is considered ideal for a true sports car in good weather conditions. 50% of the weight on the RWD and 50% on the steering.

For traction you want more on the drive wheeels. Actuallly most front wheel drive are 60% on front wheels . However, this does increase wear on those wheels and makes steering heavier. That is why there is so much to od about i4 versus V6 in handling. with I$ theres is close to 50/50% weight distirbutuion. The auto manufacturers changes nothing add the additional weight of the v6 and the steering is heavier.

If you are wealthy , I understand the ideal snow car is a Carrera 4 with Blizzacks on all four wheels.

Studded snow tires last resort, unless wehater conditions really really bad. The studs tearr up everything have bad handling excpet on ice and return poor mileage. Almost as bad as snow chains. Glad I don't deal with either naymore.

"I rented a (2005) Prius while on vacation in Arizona this year. While visiting the Grand Canyon I experienced difficult snow and ice conditions."

The problem arises when the Prius is stuck in the snow. On conventional cars, one can "rock" the vehicle back and forth to get the car moving again. The 2004-2005 Prius (at least) would not allow the wheels to spin in this situation, resulting in the car just sitting there, dead as a doornail. There was nothing mechanically wrong - but the computer would not let the driver engage the wheels.

The situation would not come up unless the Prius got stuck. You simply never encountered the proper conditions.

Some people are posting that the 2006 Prius corrects this problem, but so for no one has posted any personal experiences. Perhaps next winter...

When I lived in big snow areas, I certainly did always have a couple of 2x6's about three feet long, along with a knocked-down cardboard box or two, in my trunk. Even if only for putting on chains, those boxes often came in handy!

I also always keep, even in So California, a camp shovel, which I could always use to dig down for dirt, if really stuck.

Having other options is not the point. The question posed originally was dealing with how well the Prius does in snow situations, not how well an enterprising owner can find solutions other than the car itself.

Many people have said they drive the Prius in snow, but a few have had the "immobile" problem, which is related to the Prius.

I called a friend at San Francisco Toyota (they sell more Priuses than any other dealer in the country!) and he said he hadn't heard any complaints about this....but then, it doesn't snow very much in San Francisco. He also said he didn't think the 2007 Prius would allow disabling of the traction control, and the only change he was aware of is that the VSC system now goes on base model cars.

"I called a friend at San Francisco Toyota (they sell more Priuses than any other dealer in the country!) and he said he hadn't heard any complaints about this....but then, it doesn't snow very much in San Francisco. He also said he didn't think the 2007 Prius would allow disabling of the traction control, and the only change he was aware of is that the VSC system now goes on base model cars."

Hopefully some people will post their experiences this winter. Any Prius owners out there want to deliberately drive into snow to see if the 2006 Prius will "rock"? :surprise:

It's not likely any but the most inside engineering people at the manufacturer know what was done (if something was done) to mitigate a problem like this. I highly doubt it would perculate up to the dealers, specially one in such a temperate zone as San Fran.

Now then, if some smart tech living in the snow belt was running to ground a root-cause for claims of an owner, and if that tech made the report through channels, well then, maybe that tech would know what was happening, and what was being done.

The point is, with highly computerized complicated control systems going in our vehicles, how does the user community (or service technicians, or salespeople) end up "knowing" what the system is really doing, and if it is working per design... if it's a bug, or a "feature".

I have read here that the battery is kept at 70+% to allow head-room for charging on the go, and all of that. There has to be some place for the energy to go to, when being generated. If the battery was at 100%, that could cause problems.

That was the non-techie answer, but I am sure someone will be along and provide the specifics.

The "detailed answer" is in order to ensure the battery lasts a long time Toyota runs it from about 30% to about 80% charge.

If you allow the battery to discharge too far you run the risk of fully depleting at least one cell. This will result in reverse charging of that cell as the battery continues to discharge. This will destroy that cell eventually.

If you fully charge the battery, some cells will fully charge before the rest. They will then be "overcharged" and will heat up a lot, causing them to release pressure and loose some electrolyte. They will then loose capacity and be more susceptable to this and to the discharge problem above. Further, NIMH especially and NICD batteries too will generate a lot of heat after they reach 80% charge. This is why a "rapid charger" switches to trickle charge at about that point. Toyota wanted to avoid that extra heat and so doesn't -normally- go above 80% charge. The heat can cause the cells to overpressure and vent as above.

Sooo, the battery is operated between 30% and 70% charge, except in special cases - a) If you run out of gas you can actually discharge the traction battery down to about 20% charge. This will allow only 2-3 starts of the ICE (gas engine) so be careful if you get into this state. Note that if you run out of gas you have to put in at least three gallons before the engine will catch. The ICE is what charges the traction battery (unless you're regen. braking).

b) If you decend a long hill (say a mountain pass), the traction battery can end up with about 80% charge, and perhaps a little more - indicated by full charge on the MFD. This charging by regen braking - and it's this function that caused Toyota to leave some "room at the top" for charge to be added.